Use adapter pattern for the network deserializer

Author: jonasschnelli

src/net.cpp

@@ -571,18 +571,13 @@ bool CNode::ReceiveMsgBytes(const char *pch, unsigned int nBytes, bool& complete
     nRecvBytes += nBytes;
     while (nBytes > 0) {
         // absorb network data
-        int handled;
-        if (!m_deserializer->in_data)
-            handled = m_deserializer->readHeader(pch, nBytes);
-        else
-            handled = m_deserializer->readData(pch, nBytes);
-
+        int handled = m_deserializer->Read(pch, nBytes);
         if (handled < 0) {
             m_deserializer->Reset();
             return false;
         }
 
-        if (m_deserializer->in_data && m_deserializer->hdr.nMessageSize > MAX_PROTOCOL_MESSAGE_LENGTH) {
+        if (m_deserializer->OversizedMessageDetected()) {
             LogPrint(BCLog::NET, "Oversized message from peer=%i, disconnecting\n", GetId());
             m_deserializer->Reset();
             return false;
@@ -591,13 +586,13 @@ bool CNode::ReceiveMsgBytes(const char *pch, unsigned int nBytes, bool& complete
         pch += handled;
         nBytes -= handled;
 
-        if (m_deserializer->complete()) {
+        if (m_deserializer->Complete()) {
             // decompose a transport agnostic CNetMessage from the deserializer
             CNetMessage msg = m_deserializer->GetMessage(Params().MessageStart(), nTimeMicros);
 
             //store received bytes per message command
             //to prevent a memory DOS, only allow valid commands
-            mapMsgCmdSize::iterator i = mapRecvBytesPerMsgCmd.find(m_deserializer->hdr.pchCommand);
+            mapMsgCmdSize::iterator i = mapRecvBytesPerMsgCmd.find(msg.m_command);
             if (i == mapRecvBytesPerMsgCmd.end())
                 i = mapRecvBytesPerMsgCmd.find(NET_MESSAGE_COMMAND_OTHER);
             assert(i != mapRecvBytesPerMsgCmd.end());
@@ -639,7 +634,7 @@ int CNode::GetSendVersion() const
     return nSendVersion;
 }
 
-int TransportDeserializer::readHeader(const char *pch, unsigned int nBytes)
+int V1TransportDeserializer::readHeader(const char *pch, unsigned int nBytes)
 {
     // copy data to temporary parsing buffer
     unsigned int nRemaining = 24 - nHdrPos;
@@ -670,7 +665,7 @@ int TransportDeserializer::readHeader(const char *pch, unsigned int nBytes)
     return nCopy;
 }
 
-int TransportDeserializer::readData(const char *pch, unsigned int nBytes)
+int V1TransportDeserializer::readData(const char *pch, unsigned int nBytes)
 {
     unsigned int nRemaining = hdr.nMessageSize - nDataPos;
     unsigned int nCopy = std::min(nRemaining, nBytes);
@@ -687,15 +682,15 @@ int TransportDeserializer::readData(const char *pch, unsigned int nBytes)
     return nCopy;
 }
 
-const uint256& TransportDeserializer::GetMessageHash() const
+const uint256& V1TransportDeserializer::GetMessageHash() const
 {
-    assert(complete());
+    assert(Complete());
     if (data_hash.IsNull())
         hasher.Finalize(data_hash.begin());
     return data_hash;
 }
 
-CNetMessage TransportDeserializer::GetMessage(const CMessageHeader::MessageStartChars& message_start, int64_t time) {
+CNetMessage V1TransportDeserializer::GetMessage(const CMessageHeader::MessageStartChars& message_start, int64_t time) {
     // decompose a single CNetMessage from the TransportDeserializer
     CNetMessage msg(std::move(vRecv));
 
@@ -2708,7 +2703,7 @@ CNode::CNode(NodeId idIn, ServiceFlags nLocalServicesIn, int nMyStartingHeightIn
         LogPrint(BCLog::NET, "Added connection peer=%d\n", id);
     }
 
-    m_deserializer = MakeUnique<TransportDeserializer>(TransportDeserializer(Params().MessageStart(), SER_NETWORK, INIT_PROTO_VERSION));
+    m_deserializer = MakeUnique<V1TransportDeserializer>(V1TransportDeserializer(Params().MessageStart(), SER_NETWORK, INIT_PROTO_VERSION));
 }
 
 CNode::~CNode()

src/net.h

@@ -637,20 +637,40 @@ class CNetMessage {
  * transport protocol agnostic CNetMessage (command & payload)
  */
 class TransportDeserializer {
+public:
+    // prepare for next message
+    virtual void Reset() = 0;
+    // returns true if the current deserialization is complete
+    virtual bool Complete() const = 0;
+    // checks if the potential message in deserialization is oversized
+    virtual bool OversizedMessageDetected() const = 0;
+    // set the serialization context version
+    virtual void SetVersion(int version) = 0;
+    // read and deserialize data
+    virtual int Read(const char *data, unsigned int bytes) = 0;
+    // decomposes a message from the context
+    virtual CNetMessage GetMessage(const CMessageHeader::MessageStartChars& message_start, int64_t time) = 0;
+    virtual ~TransportDeserializer() {}
+};
+
+class V1TransportDeserializer : public TransportDeserializer
+{
 private:
     mutable CHash256 hasher;
     mutable uint256 data_hash;
-public:
     bool in_data;                   // parsing header (false) or data (true)
-
     CDataStream hdrbuf;             // partially received header
     CMessageHeader hdr;             // complete header
-    unsigned int nHdrPos;
-
     CDataStream vRecv;              // received message data
+    unsigned int nHdrPos;
     unsigned int nDataPos;
 
-    TransportDeserializer(const CMessageHeader::MessageStartChars& pchMessageStartIn, int nTypeIn, int nVersionIn) : hdrbuf(nTypeIn, nVersionIn), hdr(pchMessageStartIn), vRecv(nTypeIn, nVersionIn) {
+    const uint256& GetMessageHash() const;
+    int readHeader(const char *pch, unsigned int nBytes);
+    int readData(const char *pch, unsigned int nBytes);
+public:
+
+    V1TransportDeserializer(const CMessageHeader::MessageStartChars& pchMessageStartIn, int nTypeIn, int nVersionIn) : hdrbuf(nTypeIn, nVersionIn), hdr(pchMessageStartIn), vRecv(nTypeIn, nVersionIn) {
         Reset();
     }
 
@@ -664,25 +684,23 @@ class TransportDeserializer {
         data_hash.SetNull();
         hasher.Reset();
     }
-
-    bool complete() const
+    bool Complete() const
     {
         if (!in_data)
             return false;
         return (hdr.nMessageSize == nDataPos);
     }
-
-    const uint256& GetMessageHash() const;
-
     void SetVersion(int nVersionIn)
     {
         hdrbuf.SetVersion(nVersionIn);
         vRecv.SetVersion(nVersionIn);
     }
-
-    int readHeader(const char *pch, unsigned int nBytes);
-    int readData(const char *pch, unsigned int nBytes);
-
+    bool OversizedMessageDetected() const {
+        return (in_data && hdr.nMessageSize > MAX_PROTOCOL_MESSAGE_LENGTH);
+    }
+    int Read(const char *pch, unsigned int nBytes) {
+        return in_data ? readData(pch, nBytes) : readHeader(pch, nBytes);
+    }
     CNetMessage GetMessage(const CMessageHeader::MessageStartChars& message_start, int64_t time);
 };